The present embodiments relate to quantitative functional imaging. In particular, error information is provided for quantitative functional imaging.
Functional imaging includes positron emission tomography (PET), single photon emission computed tomography (SPECT), or other nuclear imaging. PET uses a detector ring about a patient to detect pairs of gamma rays emitted due to a collusion of a positron with an electron. The positron is generated by a radionuclide (tracer or radio-pharmaceutical) introduced into the patient. SPECT also uses introduction of a radioisotope (tracer or radio-pharmaceutical). A gamma camera is rotated about the patient to detect gamma rays emitted by the radionuclide. Both PET and SPECT provide 3D or 4D functional information, or information about uptake or other physiological function labeled by the tracer. This information is depicted in a volume image comprised out of intensity voxels typically in units of counts. The larger the intensity, the larger the uptake in the spatial region at the location of that voxel. However, this is only a relative measure, as the amount of activity concentration (activity per unit volume or activity per unit volume per unit time) has not been derived.
For quantitative functional imaging, the image now represents an estimate of the amount of uptake or activity concentration measured in units of Bq/ml or Bq/ml/s. However, any measurement has an associated error or uncertainty due the measurement method, including instrument limitations. Any error is comprised of statistical error and systematic error, which with known methods of propagation of error results in the total absolute error. The error itself may only be estimated, and that estimate itself has an associated error.